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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <!-- 求数组中所有元素的平均值 -->
    <script>
        var arr = [1, 2, 3, 4, 5];
        var sum = 0;
        
        for (let i = 0; i < arr.length; i++) {
            sum += arr[i];
        }
        var avg = sum / arr.length;
        console.log(avg);
    </script>
</body>
</html>